The second is explainshell.com. This search engine takes the exact opposite approach to ok-borg in that you get to type a shell command or sequence of commands and let explainshell parse them into their raw tokens and explain each one according to its man entry. Useful when finding snippets online but have no idea on what they do.

-exec command {} + This variant of the -exec action runs the specified command on the selected files, but the command line is built by appending each selected file name at the end; the total number of invocations of the command will be much less than the number of matched files. The command line is built in much the same way that xargs builds its command lines. Only one instance of `{}' is allowed within the command. The command is executed in the starting directory.

The last one is cmdchallenge.com.Its purpose is educational in that it assigns you challenges in order to sharpen your skills but can also act as a good host of snippets in a variety of tasks.

There's a limited number of challenges which require you to type the correct command in the interactive web based shell.

For example the challenge on

"# Print the current working directory"

requires typing pwd next to bash(0)>

If you get that right then it continues asking you to complete more 'difficult' challenges:

# You have a new challenge!# List names of all the files in the current# directory, one file per line.# bash(0)>

You can find all answers to all the challenges in the "See user submitted solutions for this challenge" area, which in this case will bring up a number of alternatives :

as already said, the number of challenges is not great, but nevertheless you can find a few advanced challenges too, for example :

"Print the file faces.txt, but only print the first instance of eachduplicate line, even if the duplicates don't appear next to each other.Note that order matters so don't sort the lines before removing duplicates."